After repairing my harddisk with testdisk, my boot partition is split up into two files (please see the attachment): a first and very tiny part containing the boot sector (Nr 1) and a second part (Nr 2).

How can I reunite the two parts and make them function as a normal boot partition? The restauration of the other partitions worked well.

Sometimes messages are normal.
It's depend on that TestDisk works Intel standard, Microsoft established another standard since Vista.
Partition not aligned on cylinder but megabyte boundaries.
That's why Analyse (displays the current partition table and is Intel standard) can provide some messages if microsoft partitions are available.
The first partition "System-reserved" is normal your boot partition and contains your start files.
The second partition has no label and is probably your Windows-partition.
Followed by your Data-Partition.
Then it's coming up an extended partition.
But infos are not available anymore, bcause you should scroll through.
Another screen from the result of Quick Search would be appreciated.